The present invention relates to a lubricating structure for an output shaft bearing portion (i.e., a bearing portion of an output shaft) in a transmission such as an automatic transmission of a motor vehicle. 2. Description of Related Art
Conventionally, as a transmission for a motor vehicle, there has hitherto been known the following one. Namely, the transmission is made up of an extension housing which is attached to an axial outside of an end wall portion of a casing main body of a transmission casing. This extension housing is provided with an output shaft bearing portion for rotatably supporting an output shaft which protrudes or projects through the end wall portion. Inside the extension housing there is contained a gear wheel such as a parking gear wheel or a vehicle speed detection gear wheel which is coupled to the output shaft.
In this kind of transmission, however, lubrication oil is supplied to the output shaft bearing portion through an oil passage which is formed inside the output shaft (see Published Unexamined Japanese Patent Application No. 80816/1990).
In the above-described conventional transmission, it is necessary to form inside the output shaft an oil passage which extends close to, or to the neighborhood of, the output shaft bearing portion. This results in difficulty in securing the strength of the output shaft.
In view of the above-described point, the present invention has an object of providing a lubrication structure in which the output shaft lubricating portion can be lubricated without forming, inside the output shaft, an oil passage for lubricating the output shaft bearing portion.
In order to attain the above and other objects, according to the present invention, there is provided a lubricating structure for an output shaft bearing portion in a transmission, comprising: an extension housing which is attached to an axial outside of an end wall portion of a casing main body of a transmission casing; an output shaft bearing portion provided in the extension housing for rotatably supporting an output shaft which protrudes through the end wall portion; a gear wheel which is contained inside the extension housing and which is coupled to the output shaft, wherein the end wall portion has formed therein an oil guide passage for guiding lubrication oil supplied to a lubricating portion inside the casing main body into the extension housing, and wherein the extension housing has formed therein a rib for guiding the lubrication oil flowing from the oil guide passage into a position in which the lubrication oil can be scraped by the gear wheel so that the output shaft bearing portion is lubricated by the lubrication oil scraped by the gear wheel.
According to the present invention, the lubrication oil that has been supplied to the lubricating portion inside the casing main body is guided by the oil guide passage and the rib, and is subsequently scraped up or lifted by the gear wheel inside the extension housing for supplying to the output shaft bearing portion. It is thus not necessary to form inside the output shaft an oil passage for lubricating the output shaft bearing portion. The strength of the output shaft can, therefore, be easily secured.